Facebook has updated its Android application to give it a little more functionality. Support for viewing profiles of your friends within the app has been added, as has the ability to view photo galleries shared by your friends.
Previously, all the Android app offered was the ability to view a news feed - doing almost anything else would open up a browser window with Facebook's (admittedly pretty good) mobile site. With the update, that occurrence has been reduced, but still happens if you try and view your inbox, or events.
To grab the update, you can hit the Android market on your handset, and go to "my downloads", which will then list all the apps that have updates waiting. Select Facebook, and follow the prompts on-screen to download the app.